Sandwich structure power supply module

ABSTRACT

A sandwich structure power supply module, having: an inductor pack having a first inductor and a second inductor; a bottom PCB (Printed Circuit Board) at the bottom of the sandwich structure power supply module; a top PCB on top of the inductor pack; a connector coupled between the bottom PCB and the top PCB, coupling solder pads on the bottom PCB to solder pads on the top PCB; and a first and a second power device chips on top of the top PCB, wherein the first power device chip and the second power device chip respectively has at least one pin coupled to the first inductor and the second inductor via the top PCB; wherein each inductor comprises one winding having a first end and a second end bent to and extended at a plane perpendicular to an axis along a length of the winding.

TECHNICAL FIELD

The present invention generally relates to electrical components, and more particularly but not exclusively relates to power supply modules.

BACKGROUND

Power converter, as known in the art, converts an input power to an output power for providing a load with required voltage and current. Multi-phase power converter comprising a plurality of paralleled power stages operating out of phase has lower output ripple voltage, better transient performance and lower ripple-current-rating requirements for input capacitors. They are widely used in high current and low voltage applications, such as server, microprocessor.

With the development of modern GPUs (Graphics Processing Units), and CPUs (Central Processing Units), increasingly high load current is required to achieve better processor performance. However, the size of microprocessor needs to become smaller. Higher current and smaller size put more challenges to the heat conduction. Therefore, high-power density and high-efficiency power converters with excellent heat dissipation path are necessary.

SUMMARY

It is an object of the present invention to provide a sandwich structure power supply module with inductors, power switches and drivers mounted and integrated in a small size power supply module.

The embodiments of the present invention are directed to a sandwich structure power supply module, comprising: an inductor pack having a first inductor and a second inductor; a bottom PCB (Printed Circuit Board) at the bottom of the sandwich structure power supply module; a top PCB on top of the inductor pack; a connector connected between the bottom PCB and the top PCB, wherein the connector has a plurality of metal pillars respectively connecting solder pads on the bottom PCB to solder pads on the top PCB; and a first power device chip and a second power device chip on top of the top PCB, wherein the first power device chip has at least one pin connected to the first inductor via the top PCB, and the second power device chip has at least one pin connected to the second inductor via the top PCB; wherein each inductor comprises one winding having a first end and a second end, wherein the first end and the second end of each winding are bent to and extended at a plane perpendicular to an axis along a length of the winding.

The embodiments of the present invention are directed to an inductor pack used with a sandwich structure power supply module, comprising: a magnetic core having a first magnetic core part and a second magnetic core part, wherein the first magnetic core part and the second magnetic core part are assembled to have N passageways between the first magnetic core part and the second magnetic core part, wherein N is an integer, and N>1; and N windings respectively passing through the N passageways between the first magnetic core part and the second magnetic core part, wherein each winding has a first end and a second end, and wherein each end of the windings is bent to and extended at a plane perpendicular to an axis along a length of the winding.

The embodiments of the present invention are directed to a sandwich structure power supply module, comprising: an inductor pack having N inductors, wherein N is an integer, and N>1; a top PCB (Printed Circuit Board) on top of the inductor pack; and N power device chips on top of the top PCB, wherein each one of the power device chips has one or more than one pins connected to a first end of one associated inductor of the inductor pack via the top PCB; wherein each inductor comprises a winding having two ends, and wherein the end of each winding connected to the top PCB is bent to and extended at a plane perpendicular to an axis along a length of the winding.

The sandwich structure power supply module in the present invention: (1) could save PCB (Printed Circuit Board) footprint compared to the prior art tiled module structure, which improves load current/power density; (2) could minimize the output current trace impedance on PCB and mainly deliver output current through inductor legs to achieve high-efficiency; and (3) with the power device chips on top and inductor pack on bottom structure could largely benefit from the top-side cooling system which is normally adopted by GPU, CPU, ASIC (Application Specific Integrated Circuit) systems.

The inductor pack in the present invention: 1) takes the most advantage of inductor area and thus maximize the inductance value/saturation current; 2) adopts hybrid magnetic core materials to avoid the sharp drop of inductance value at high saturation current. Overall, the inductor pack in the present invention is designed to have low DCR, high inductance at low current for high efficiency, low inductance at high current for good transient performance, and external ground legs for high current return path.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be further understood with reference to the following detailed description and the appended drawings, wherein like elements are provided with like reference numerals. The drawings are only for illustration purpose. They may only show part of the devices and are not necessarily drawn to scale.

FIG. 1 schematically shows a prior art multi-phase power converter 10 which comprises a controller 101, N power devices 103 and N inductors L1 for supplying power to a load 104.

FIG. 2 shows a sandwich structure power supply module 20 for a dual-phase power converter in accordance with an embodiment of the present invention.

FIG. 3 shows the disassemble view of an inductor pack 30 in accordance with an embodiment of the present invention.

FIG. 4 shows the disassemble view of an inductor pack 40 in accordance with an embodiment of the present invention.

FIG. 5 shows the disassembled view of an inductor pack 50 in accordance with an embodiment of the present invention.

FIG. 6 shows a magnetic core 60 in accordance with an embodiment of the present invention.

FIG. 7 shows a magnetic core 70 in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

In the present disclosure, numerous specific details are provided, such as examples of electrical circuits and components, to provide a thorough understanding of embodiments of the invention. Persons of ordinary skill in the art will recognize, however, that the invention can be practiced without one or more of the specific details. It is noted that, for purposes of illustrative clarity, certain elements in the drawings may not be drawn to scale. In other instances, well-known details are not shown or described to avoid obscuring aspects of the invention.

FIG. 1 schematically shows a multi-phase power converter 10 which comprises a controller 101, N power devices 103 and N inductors L1 for supplying power to a load 104, wherein N is an integer, and N>1. Each power device 103 and one inductor L1 represent one power stage, i.e., one phase 102 of the power converter 10, as shown in FIG. 1. Each power device 103 comprises power switches M1, M2 and a driver DR1 for driving the power switches M1 and M2. The controller 101 provides N phase control signals 105-1˜105-N respectively to N power devices 103 to control the N phases 102 working out of phase, i.e., the inductors L1 sequentially absorb power from the input source and sequentially deliver power to the load 104. It should be noticed that the outputs of all phases as shown in FIG. 1 are connected to work as a multi-phase converter. However, each phase output may be separated to work as multiple independent converters which could have different output voltage levels for different load demands.

The power stage 102 with Buck topology is shown in FIG. 1 for example. Persons of ordinary skill in the art should appreciate that power stages with other topologies, like Boost topology, Buck-Boost topology could also be adopted in a multi-phase power converter.

The inductors L1 could be implemented by one or a few coupled inductors or could be implemented by N single inductors.

When N=2, the multi-phase power converter 10 is used as a dual-phase power converter or two separate single-phase converters.

FIG. 2 shows a sandwich structure power supply module 20 for a dual-phase power converter in accordance with an embodiment of the present invention. The power supply module 20 may serve as the power stage 102 of FIG. 1, with N=2. The sandwich structure power supply module 20 comprises: a bottom PCB 201 at the bottom of the sandwich structure power supply module 20; an inductor pack 206 having two inductors located on the bottom PCB 201, wherein each inductor has a first end and a second end; a top PCB 202 on the top of the inductor pack 206; a connector 204 placed between the bottom PCB 201 and the top PCB 202, wherein the connector 204 has a plurality of metal pillars 205 respectively connecting solder pads on the bottom PCB to solder pads on the top PCB; and two power device chips 203 on the top of the top PCB 202, wherein each one of the power device chips 203 has one or more than one pins connected to the second end of one inductor of the inductor pack 206 via the top PCB 202; wherein each inductor comprises a winding 207 having ends folded to a plane perpendicular to an axis along a length of the winding 207.

In FIG. 2, the power supply module 20 further comprises the discrete components 208 located on the top PCB 202. The discrete components 208 comprise resistors and capacitors of the power converter 10, like the input capacitors at the input terminal to provide pulse current, the filter capacitors and resistors for driver and internal logic circuits power supplies, etc.

In one embodiment, the metal pillars 205 comprises copper pillars for soldering the bottom PCB 201 to the top PCB 202. Persons of ordinary skill in the art should appreciate that the metal pillars 205 could be made of any known material for soldering one PCB to another PCB.

The power supply module 20 is utilized to a mainboard to supply power to the devices on the mainboard. The bottom PCB 201 is soldered to the mainboard to connect the necessary pins of the power supply module 20 to the mainboard. In some embodiments, the bottom PCB 201 could be saved. The connector 204 and the inductor pack 206 are soldered to the mainboard directly.

In the present invention, the inductors and the power device chips are mounted to save the footprint on a PCB integrating the power converter 10 and the devices powered by the power converter 10. Each power device chip 203 integrates the power device 103 in FIG. 1, which comprises the power switches M1, M2, the driver DR1, and further integrates some auxiliary circuits not shown in FIG. 1. The pins of the power device chips 203 are connected to the solder pads on the bottom PCB 201 via the top PCB 202, the inductor pack 206 and the connector 204, to make sure that all the necessary signals could be obtained from the bottom PCB 201. Furthermore, for the signals with large current, like ground reference, the power supply module 20 provides metal layers 209. The metal layers 209 solders the top PCB 202 to the bottom PCB 201. The metal layer 209 coats part of a magnetic core of the inductor pack 206. The location of the metal layer 209 is determined by the location of ground reference pins of the power device chips 203. In the example of FIG. 2, since the metal layers 209 are placed at the side of the inductor pack 206, the ends of the metal layers 209 are bent to produce tabs close to the ground reference pins of the power device chips 203, so that to carry high current in the horizontal direction only through metal tabs instead of PCB traces which lowers conduction loss and improve efficiency.

FIG. 3 shows the disassembled view of an inductor pack 30 in accordance with an embodiment of the present invention. The inductor pack 30 may be served as the inductor pack 206 in FIG. 2. As shown in FIG. 3, the inductor pack 30 comprises: a magnetic core having a first magnetic core part 301 and a second magnetic core part 302, wherein the first magnetic core part 301 and the second magnetic core part 302 are assembled to have two passageways 303-1 and 303-2 at a planer where the first magnetic core part 301 and the second magnetic core part 302 are aligned; and two windings 304-1 and 304-2 respectively passing through two passageways 303-1 and 303-2 between the first magnetic core part 301 and the second magnetic core part 302.

In the embodiment of FIG. 3, the passageways 303-1 and 303-2 have a depth along an axis A parallel to the bottom PCB 201 and the top PCB 202 as shown in FIG. 2.

In the embodiment of FIG. 3, the winding 304-1 has a first end 304-3 bent 90 degrees to cover a surface of the magnetic core and extended to the top PCB 202 to be soldered to the top PCB 202, and a second end 304-5 bent 90 degrees to cover a surface of the magnetic core and extended to the bottom PCB 201 to be soldered to the bottom PCB 201, and wherein the first end 304-3 and the second end 304-5 of the winding 304-1 are extended at a plane perpendicular to an axis along the depth of the passageways 303-1 and 303-2 of the magnetic core. Similarly, the winding 304-2 has a first end 304-4 bent 90 degrees to cover a surface of the magnetic core and extended to the top PCB 202 to be soldered to the top PCB 202, and a second end 304-6 bent 90 degrees to cover a surface of the magnetic core and extended to the bottom PCB 201 to be soldered to the bottom PCB 201, and wherein the first end 304-4 and the second end 304-6 of the winding 304-2 are extended at a plane perpendicular to an axis along the depth of the passageways 303-1 and 303-2 of the magnetic core.

In the embodiment of FIG. 3, the magnetic core has a first magnetic core part 301 and a second magnetic core part 302 which are asymmetrical, wherein the first magnetic core part 301 is in a planar shape and the second magnetic core part 302 has two trenches, and wherein each of the passageways 303-1, 303-2 is respectively formed by a trench of the second magnetic core 302 and a surface 301-1 of the first magnetic core 301.

In the embodiment of FIG. 3, the metal layers 305-1 and 305-2 have a L-shape. The metal layers 305-1 and 305-2 are configured to solder the top PCB 202 to the bottom PCB 201. The ends of the metal layers 305-1 and 305-2 for soldering the top PCB 202 are bent 90 degrees and extended to produce tabs to be soldered to the ground reference pins of the power device chips 203 via the top PCB 202 with minimized PCB trace impedance inside the top PCB.

FIG. 4 shows the disassembled view of an inductor pack 40 in accordance with an embodiment of the present invention. The inductor pack 40 may be served as the inductor pack 206 in FIG. 2. As shown in FIG. 4, the inductor pack 40 comprises: a magnetic core having a first magnetic core part 401 and a second magnetic core part 402, wherein the first magnetic core part 401 and the second magnetic core part 402 are assembled to have two passageways 403-1 and 403-2 at a planer where the first magnetic core part 401 and the second magnetic core part 402 are aligned; and two windings 404-1 and 404-2 respectively passing through two passageways 403-1 and 403-2 between the first magnetic core part 401 and the second magnetic core part 402.

In the embodiment of FIG. 4, the passageways 403-1 and 403-2 have a depth along an axis B perpendicular to the bottom PCB 201 and the top PCB 202 if adopted by the power supply module 20 in FIG. 2.

In the embodiment of FIG. 4, the winding 404-1 has a first end 404-3 bent 90 degrees to cover a surface of the magnetic core and extended along a surface of the top PCB 202 to be soldered to the top PCB 202, and a second end 404-5 bent 90 degrees to cover a surface of the magnetic core and extended along a surface of the bottom PCB 201 to be soldered to the bottom PCB 201, and wherein the first end 404-3 and the second end 404-5 of the winding 404-1 are extended at a plane perpendicular to an axis along the depth of the passageways 403-1 and 403-2 of the magnetic core. Similarly, the winding 404-2 has a first end 404-4 bent 90 degrees to cover a surface of the magnetic core and extended along a surface of the top PCB 202 to be soldered to the top PCB 202, and a second end 404-6 bent 90 degrees to cover a surface of the magnetic core and extended along a surface of the bottom PCB 201 to be soldered to the bottom PCB 201, and wherein the first end 404-4 and the second end 404-6 of the winding 404-2 are extended at a plane perpendicular to an axis along the depth of the passageways 403-1 and 403-2 of the magnetic core.

In some embodiments, the second end 404-5 of the windings 404-1, and the second end 404-6 of the windings 404-2 are not bent. Whether the second ends of the winding are bent or not, and the locations, shapes of the second ends of the windings, are determined by the locations of the associated solder pads on the bottom PCB of the power supply module, or the associated solder pads on the mainboard if the bottom PCB is saved.

In the embodiment of FIG. 4, the magnetic core has a first magnetic core part 401 and a second magnetic core part 402 which are asymmetrical, wherein the first magnetic core part 401 is in a planar shape and the second magnetic core part 402 has two trenches, and wherein each of the passageways 403-1, 403-2 is respectively formed by a trench of the second magnetic core 402 and a surface 401-1 of the first magnetic core 401.

In the embodiment of FIG. 4, the metal layers 405-1 and 405-2 have a C shape. The metal layers 405-1 and 405-2 are configured to solder the top PCB 202 to the bottom PCB 201. The ends of the metal layers 405-1 and 405-2 for soldering the bottom PCB 201 are bent 90 degrees and extended to produce tabs to be soldered to the bottom PCB 201 with minimized PCB trace impedance inside the bottom PCB 201. Also, the ends of the metal layers 405-1 and 405-2 for soldering the top PCB 202 are bent 90 degrees and extended to produce tabs to be soldered to the ground reference pins of the power device chips 203 via the top PCB 202 with minimized PCB trace impedance inside the top PCB 202.

FIG. 5 shows the disassembled view of an inductor pack 50 in accordance with an embodiment of the present invention. The inductor pack 50 may be served as the inductor pack 206 in FIG. 2. As shown in FIG. 5, the inductor pack 50 comprises: a magnetic core having a first magnetic core part 501 and a second magnetic core part 502, wherein the first magnetic core part 501 and the second magnetic core part 502 are assembled to have two passageways 503-1 and 503-2 at a planer where the first magnetic core part 501 and the second magnetic core part 502 are aligned; and two windings 504-1 and 504-2 respectively passing through two passageways 503-1 and 503-2 between the first magnetic core part 501 and the second magnetic core part 502.

In the embodiment of FIG. 5, the passageways 503-1 and 503-2 have a depth along an axis B perpendicular to the bottom PCB 201 and the top PCB 202 if adopted by the power supply module 20 in FIG. 2.

In the embodiment of FIG. 5, the metal layer 505 has a C shape. The metal layer 505 is configured to solder the top PCB 202 to the bottom PCB 201. The end of the metal layer 505 for soldering the bottom PCB 201 are bent 90 degrees and extended to produce tabs to be soldered to the bottom PCB 201 with minimized PCB trace impedance inside the bottom PCB 201. Also, the end of the metal layer 505 for soldering the top PCB 202 are bent 90 degrees and extended to produce tabs to be soldered to the ground reference pins of the power device chips 203 via the top PCB 202 with minimized PCB trace impedance inside the top PCB 202. In the example of FIG. 5, the middle part of the metal layer 505 are extended to both sides to lower the impedance of the metal layer 505.

Compared with the inductor pack 40 in FIG. 4, the inductor pack 50 in FIG. 5 has one metal layer 505 for soldering the ground pins from the top PCB 202 to the bottom PCB 201. Since the area for another ground metal layer as in FIG. 4 is saved, the ends of the windings in the embodiment of FIG. 5 extend to larger areas at the top and the bottom of the inductor pack 50, which makes the power device chips 203 have more flexibility to configure pins.

The magnetic core having a first magnetic core part 501 and a second magnetic core part 502 in the embodiment of FIG. 5 is similar to the magnetic core in the embodiment of FIG. 4, and is not described here for brevity.

FIG. 6 shows a magnetic core 60 in accordance with an embodiment of the present invention. In FIG. 6, the magnetic core 60 comprises a first magnetic core part 601 and a second magnetic core part 602 which are symmetrical, wherein each one of the magnetic core parts has two trenches. When the magnetic core 60 is adopted by the inductor pack 30 in FIG. 3, the inductor pack 40 in FIG. 4, or the inductor pack 50 in FIG. 5, each passageway for passing a winding is formed by a trench of the first magnetic core part 601 and a trench of the second magnetic core part 602.

FIG. 7 shows a magnetic core 70 in accordance with an embodiment of the present invention. In FIG. 7, the magnetic core 70 comprises a first magnetic core part 701, a second magnetic core part 702 and third magnetic core parts 703-1-703-3. The first magnetic core part 701, the second magnetic core part 702 and the third magnetic core parts 703-1 and 703-2 forms a passageway 704-1. The first magnetic core part 701, the second magnetic core part 702 and the third magnetic core parts 703-2 and 703-3 forms a passageway 704-2. More passageways could be formed when there are more third magnetic core parts. The first magnetic core part 701, the second magnetic core part 702 and the third magnetic core parts 703-1-703-3 could be made of different materials to provide a more flexible inductance-current curve.

In some embodiments of the present invention, the magnetic core parts of the magnetic core may be made of the same material, but have different geometries and/or percent composition to meet an inductance-current requirement of a target inductance profile, e.g., high inductance at low currents and low inductance at high currents. High inductance at low currents allows for higher efficiency, while low inductance at high currents allows for better transient response. In some embodiments, the magnetic core parts of the magnetic core may be made of different materials, like ferrite, iron powder, and any other suitable magnetic material to obtain a target inductance profile.

The inductor pack 30 in FIG. 3, the inductor pack 40 in FIG. 4 and the inductor pack 50 in FIG. 5 show magnetic cores with two windings respectively passing through two passageways of the magnetic cores for illustration. Persons of ordinary skill in the art should appreciate that the magnetic cores of the present invention could have any number of passageways and the corresponding windings according to the application requirement, like, one, or more than two.

In some embodiments, a gap may exist between the magnetic core parts of the magnetic core to form a coupled inductor. In some embodiments, independent inductors are formed with no gap between the magnetic core parts.

In the present invention, to make the inductor packs have planar surfaces, the windings and the metal layers that cover the surfaces of the magnetic cores are damascened into the magnetic core surfaces as shown in FIGS. 3 and 4.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. It should be understood, of course, the foregoing disclosure relates only to a preferred embodiment (or embodiments) of the invention and that numerous modifications may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims. Various modifications are contemplated and they obviously will be resorted to by those skilled in the art without departing from the spirit and the scope of the invention as hereinafter defined by the appended claims as only a preferred embodiment(s) thereof has been disclosed. 

What is claimed is:
 1. A sandwich structure power supply module, comprising: an inductor pack having a first inductor and a second inductor; a bottom PCB (Printed Circuit Board) at the bottom of the sandwich structure power supply module; a top PCB on top of the inductor pack; a connector connected between the bottom PCB and the top PCB, wherein the connector has a plurality of metal pillars respectively connecting solder pads on the bottom PCB to solder pads on the top PCB; and a first power device chip and a second power device chip on top of the top PCB, wherein the first power device chip has at least one pin connected to the first inductor via the top PCB, and the second power device chip has at least one pin connected to the second inductor via the top PCB; wherein each inductor comprises one winding having a first end and a second end, wherein the first end and the second end of each winding are bent to and extended at a plane perpendicular to an axis along a length of the winding.
 2. The sandwich structure power supply module of claim 1, further comprising: a magnetic core having a first magnetic core part and a second magnetic core part, wherein the first magnetic core part has a planar shape, and the second magnetic core part has two trenches, and wherein two passageways are formed by a surface of the first magnetic core part and the two trench of the second magnetic core part; and two windings respectively passing through the two passageways between the first magnetic core part and the second magnetic core part.
 3. The sandwich structure power supply module of claim 2, wherein: the passageways have a depth along an axis parallel to the bottom PCB and the top PCB.
 4. The sandwich structure power supply module of claim 2, wherein: the passageways have a depth along an axis perpendicular to the bottom PCB and the top PCB.
 5. The sandwich structure power supply module of claim 1, further comprising at least one metal layer, wherein the at least one metal layer is in a C-shape with a first end bent to be extended and soldered to a bottom surface of the top PCB, and a second end bent to be extended and soldered to a top surface of the bottom PCB, and wherein the second end of the at least one metal layer is connected to ground reference pins of the power device chips via the top PCB.
 6. The sandwich structure power supply module of claim 1, further comprising at least one metal layer, wherein the at least one metal layer is bent in a L-shape with a first end bent to be extended and soldered to a bottom surface of the top PCB, and a second end soldered to the bottom PCB, and wherein the first end of the at least one metal layer is connected to ground reference pins of the power device chips via the top PCB.
 7. An inductor pack used with a sandwich structure power supply module, comprising: a magnetic core having a first magnetic core part and a second magnetic core part, wherein the first magnetic core part and the second magnetic core part are assembled to have N passageways between the first magnetic core part and the second magnetic core part, wherein N is an integer, and N>1; and N windings respectively passing through the N passageways between the first magnetic core part and the second magnetic core part, wherein each winding has a first end and a second end, and wherein each end of the windings is bent to and extended at a plane perpendicular to an axis along a length of the winding.
 8. The inductor pack of claim 7, wherein the first magnetic core part has a planar shape, and the second magnetic core part has N trenches, and wherein each passageway is formed by a surface of the first magnetic core part and a trench of the second magnetic core part.
 9. The inductor pack of claim 7, wherein each of the first magnetic core part and the second magnetic core part has N trenches, each passageway is formed by a trench of the first magnetic core and a trench of the second magnetic core part.
 10. The inductor pack of claim 7, wherein each inductor of the inductor pack provides a high inductance at low currents and a low inductance at high currents.
 11. The inductor pack of claim 7, further comprising a plurality of third magnetic core parts between the first magnetic core part and the second magnetic core part, wherein the first magnetic core part and the second magnetic core part have a planar shape, and wherein each passageway is formed by a surface of the first magnetic core part, a surface of the second magnetic core part, and two adjacent third magnetic core parts.
 12. A sandwich structure power supply module, comprising: an inductor pack having N inductors, wherein N is an integer, and N>1; a top PCB (Printed Circuit Board) on top of the inductor pack; and N power device chips on top of the top PCB, wherein each one of the power device chips has one or more than one pins connected to a first end of one associated inductor of the inductor pack via the top PCB; wherein each inductor comprises a winding having two ends, and wherein the end of each winding connected to the top PCB is bent to and extended at a plane perpendicular to an axis along a length of the winding.
 13. The sandwich structure power supply module of claim 12, further comprising: a bottom PCB at the bottom of the sandwich structure power supply module; and a connector having a plurality of metal pillars respectively connecting the solder pads on the top PCB to the solder pads on the bottom PCB.
 14. The sandwich structure power supply module of claim 12, wherein the inductor pack comprises: a magnetic core having a first magnetic core part and a second magnetic core part, wherein the first magnetic core part and the second magnetic core part are assembled to have N passageways between the first magnetic core part and the second magnetic core part; and N windings respectively passing through the N passageways between the first magnetic core part and the second magnetic core part.
 15. The sandwich structure power supply module of claim 12, wherein the inductor pack comprises: a magnetic core having a first magnetic core part, a second magnetic core part and third magnetic core parts, wherein the first magnetic core part, the second magnetic core part and the third magnetic core parts are assembled to have N passageways between the first magnetic core part and the second magnetic core part; and N windings respectively passing through the N passageways between the first magnetic core part and the second magnetic core part.
 16. The sandwich structure power supply module of claim 12, wherein the windings have a depth along an axis parallel to the top PCB.
 17. The sandwich structure power supply module of claim 16, wherein each winding has an end bent up to be connected to one or more than one solder pads on the top PCB, and wherein the end connected to the top PCB of each winding is extended at a plane perpendicular to an axis along the depth of the windings.
 18. The sandwich structure power supply module of claim 12, wherein the windings have a depth along an axis perpendicular to the top PCB.
 19. The sandwich structure power supply module of claim 18, wherein each winding has an end connected to one or more than one solder pads on the top PCB, and wherein the end of each winding connected to the top PCB is extended at a plane perpendicular to an axis along the depth of the windings.
 20. The sandwich structure power supply module of claim 18, wherein each winding has an end connected to one or more than one solder pads on the top PCB, and wherein the end of each winding connected to the top PCB is extended at a plane perpendicular to an axis along the depth of the windings. 